In recent years, with the advent of the advanced information society, optical communication networks in which optical fibers are used for transmission lines have been gradually developed. In the optical communication networks, using short optical pulses that can be superimposed enables a large volume of data to be transmitted at high speed. Further, the shorter a temporal length of an optical pulse becomes, the more it becomes possible to transmit the large volume of data at high speed.
It is to be noted that velocities of lights slightly differ from one another in a medium such as an optical fiber, depending on wavelengths, and wavelength dispersion, to be precise, group velocity dispersion occurs. That is to say, the shorter a temporal length of an optical pulse becomes, the more easily dispersion occurs in a wavelength, thereby restricting a transmission rate and a transmission distance to impede high-speed communication.
For this reason, in the optical communication networks where data are transmitted by controlling lights in a femtosecond time domain (10−15 to 10−12 seconds), a dispersion compensator is imperative for compensating dispersion such as spread of or variation in a pulse width.
With this, for instance, dispersion compensators each using a chirped fiber grating (e.g., refer to Patent Reference 1) have been proposed.
Patent Reference 1: Japanese Unexamined Patent Application Publication No. 2000-137197